EXTRAORDINARY CASE REPORT: PDF OnlyMalignant Melanoma within an Intradermal NevusTajima, Yasuo M.D.; Nakajima, Tohru M.D.; Sugano, Isamu M.D.; Nagao, Koichi M.D.; Kondo, Yoichiro M.D.Author Information From the Department of Surgical Pathology (Y.T., T.N., I.S., K.N.), Teikyo University School of Medicine, Ichihara Hospital, Ichihara; and the Department of Pathology (Y.K.), Chiba University School of Medicine, Chiba, Japan. The American Journal of Dermatopathology: June 1994 - Volume 16 - Issue 3 - p 301-306 Buy Abstract We describe a case of malignant “dermal” melanoma that arose within a preexisting intradermal nevus. Clinically, the lesion had recently enlarged. Histologically, two patterns were noted. One was an intradermal nevus in the upper portion of the dermis; the other was a deeper nodule composed of malignant neoplastic cells that extended into the reticular dermis. No melanocytic epidermal junctional activity was noted. Despite careful clinical investigation, no alternative primary source was found. Neoplastic transformation of the intradermal nevus without junctional activity is our proposed interpretation of the lesion's histology. Immunohistochemical stains demonstrated that the deeper dermal neoplastic cells were positive for both HMB-45 and PCNA, whereas the superficial nevoid-appearing cells were negative; these findings support our postulate that this melanoma arose within an intradermal nevus. It is important to distinguish this neoplasm from other diagnostic possibilities, including a metastatic lesion originating from another site. © Lippincott-Raven Publishers.